Burglar alarm not working after power failure

not a car or truck it is a home alarm by Honeywell
no model number told
8SP400A?????
it needs service, if the main pad is dead. got wet is top cause
or just too old
this manual match up free

https://prod-edam.honeywell.com/content/dam/honeywell-edam/hbt/en-us/documents/manuals-and-guides/user-manuals/IE1-0040-Rev1-engineer%2520pdf.pdf?download=false

Try here
http://www.alarm-supplies.com/user%20manuals/optima-accenta%20g3.pdf

I'm not familiar with accenta plus alarms but if your motion detector is picking you up then your panel is beeping sounds like the motion is programmed incorrectly.

Default code for ade accenta panels is 0123

Your Sonata is equipped with a "Keyless Entry & Burglar Alarm" system. When the Burglar Alarm is activated, it KILLS the starting system through the used of a relay called the "Burglar Alarm Relay". This mode prevents engine starting with the key.
Solution #1
Disarm the system with the Keyless Remote (key fob) If you don't have this remote (or its battery is dead) replace the battery & try disarming again.
Solution #2
Enter the vehicle & insert the key in the ignition and turn the ignition switch to 'RUN'. Wait 3 to 5 minutes until the alarm stops. You should then be able to start the engine.

Have a qualified/certified Hyundai Service Technician properly diagnose this issue.

The 'Keyless Entry & Burglar Alarm System" is activated. You must 'Disarm' the system using the Keyless Entry Remove (Key Fob) to "Reset" the system. The reason the engine won't start is due to the burglar alarm - it has a "Starter Kill" circuit which is activated when the alarm is activated. The alarm must be DEactivated to DEactivate the 'Starter Kill' circuit.
Another way to start the engine is to get in the car, put the key in the ignition and turn it to 'ON" and wait 3 to 5 minutes until the emergency flashers stop/turn off. Afterward, you should be able to start the engine. NOTE: This does NOT reset the burglar alarm. It will go off again when you enter the vehicle without using the remote/key fob.

> Since power ws restored, I hav a low battery alarm for about 3 days.
The charge circuit probably only supplies a tiny charge current to prevent overcharging of the main battery and I suspect the original is a NiCad and has likely lost a cell or two (shorted; it's common with them) over that fairly long period.
Replacing it with either Lithium Ion or NiMh rechargeables with a honest voltage rating (*some aren't) is a good move; neither of these are as prone to failure as NiCad is. Don't be surprised if you still have a 'low battery' alert for several days since these batteries rarely have a full charge when shipped.
*So-called '9V' block batteries are, except for rare batteries, actually 8.4 or even only 7.2 volts. I have some instruments that indicate 'Low battery' with either of these even when fully charged.

Tell me what brand your alarm is and I can help you with the beeping. Usually if you hit # it will silence the beeping for 24 hours. Something you can try is finding your main control box. Its usually located in the garage or in a closet. It is tan and 6 x6. First disconnect the battery inside the control box by jiggling off the black/red leeds. Then unplug the power supply. Wait five minutes. Reconnect the battery and plug in the control box. This is completely powering your system down and then repowering it up-essentially "re booting." If this does not correct the issue, give me the brand and I can further help you.

I am not familiar with the Accenta alarm, but would like to help you. Is this an alarm to tell if your unit has been tampered with? Is this a password code to get you into your machine? With a little more info I may be able to help you out of your bind.
David